Sticking around is brave, you're right. But there are two ways of solving a seemingly intractable problem.
One is to punch your ticket. This is a rational solution, given your view of your situation. But it's also messy (bit of an understatement). You love your children, you don't really want them to grow up without their mum. And a whole host of other reasons it's really difficult to see right now, like the hole your not being around will leave (massive).
The other is to go further in but with some backup. If you're struggling with your CPN madeup and accessing someone competent to talk to, MIND could offer you an advocate to go with you and speak to your GP. I know from personal experience that having someone with you will make a difference to how you feel and how you're treated.
Link to MIND advocacy is here for you.
In the short term, I'd highly recommend you call the Samaritans on 08457 909090.
You may think it's pointless, but trust me, the actual act of deciding to call, dialling the number, then hovering your finger (for ages) over the call button before just saying "fuck it" then pressing, is a big thing.
Why? Because on some deep level there will be an acknowledgement of "shit, I'm really in trouble here; look what I'm doing actually speaking to a real person about what I'm thinking about doing". And that just may shift you enough to seek further, different help in working hours.
Thing is, you already are brave madeup. You're dealing with a lot of pain, it sounds like you don't feel anything is working for you, yet you're choosing to continue. I'm not bullshitting you here, facing known pain really is hardcore, and shows mettle. Could you take some of that grit, do you think, and reach out a little further?
Will you call the Samaritans? Please? 